Immune memory response induced in vitro by recombinant hepatitis B surface antigen challenge 13-18 years after primary vaccination

The question of whether booster doses are required to maintain long‐term protection against hepatitis B virus (HBV) after primary vaccination remains to be determined. Thus, the aim of this study was to evaluate the immune memory responses to hepatitis B surface antigen (HBsAg) challenge in vaccinated individuals through an in vitro‐specific stimulation assay. Peripheral blood mononuclear cells (4 × 106 cells/ml) were stimulated with 50 ng/ml of recombinant HBsAg. In vitro anamnestic antibody responses, as shown by detection of high avidity antibody in culture supernatants, were found 13–18 years after primary vaccination and were not correlated with serum antibodies (r = −0.177; P = 0.377). In addition, the findings from this study indicate that immune memory against hepatitis B was well preserved in 40.0% and 60.0% of vaccinees with anti‐HBs levels less than 10 IU/L or lacking serum antibodies altogether, respectively. In conclusion, the data suggest the presence of immunological memory in vaccinated individuals, including those who showed anti‐HBs